(a) Field of the Invention
This invention relates to hybrid vehicles.
(b) Description of the Related Art
A generally known electrical system configuration of a hybrid vehicle includes a generator connected to an engine, an electric motor connected to a drive wheel and first and second inverters interposed between the generator and the electric motor to covert AC power to DC power or vice versa. In such a configuration, AC power generated in the generator is converted to DC power by the first inverter, the DC power is reconverted to AC power by the second inverter and the AC power is then fed to the electric motor.
However, since in the above configuration two inverters are interposed between the generator and the electric motor, this causes a problem of large power loss.
A hybrid vehicle is disclosed as an example of improvement for the above problem in PCT Publication WO 2005/105511 A1. The hybrid vehicle has an electrical system configuration in which a matrix converter for directly converting AC power to AC power is interposed between a generator and an electric motor.
The hybrid vehicle with the above configuration, however, has the following problems. Specifically, the electrical system of the hybrid vehicle is configured so that a matrix converter is interposed between a first rotary electric machine and a second rotary electric machine and a battery is connected via an inverter to an electrical path branched between the matrix converter and the second rotary electric machine. Therefore, the first rotary electric machine is connected to the battery via the inverter and the matrix converter and the second rotary electric machine is connected to the battery via the inverter only.
According to the above configuration, when electric power from the battery is fed to drive (activate) the first rotary electric machine, it is also fed to the second rotary electric machine. Thus, when the second rotary electric machine is already doing work, its torque output is increased. On the other hand, when the second rotary electric machine is stopped, an unnecessary torque is generated.
These problems occur where the first rotary electric machine is a generator connected to an engine and is used as a starter for the engine. Specifically, when driving electric power is fed from the battery through the inverter and the matrix converter to the generator (first rotary electric machine) in order to start the engine, driving electric power is also fed to the electric motor that is the second rotary electric machine. This causes the electric motor to generate an unnecessary torque output or unnecessarily increase the torque output.